As shown in FIG. 1, the existing drum washing machine comprises a shell 1′ which forms an exterior appearance, as washing bucket 2′ for containing washing water is provided in the shell 1′, a drum 3′ for washing and dewatering the laundry is rotatablly provided in the washing bucket 2′, a drive motor connected to a rotatable shaft of the drum is provided behind the washing bucket. A door for throwing in or taking out laundry is arranged at a front surface of the shell, and a stand for supporting the rotatable shaft of the drum is arranged behind the washing bucket. An upper portion of the washing bucket 2′ is suspended inside the shell 1′ by a spring 4′, and a shock absorber 5′ for absorbing a vibration transmitted from the drum 3′ to the washing bucket 2′ is arranged below the washing bucket 2′.
It is known to persons skilled in the art that the shock absorber of the drum type washing machine is limited to effectively absorb in small vibration absorbing and large vibration, because the vibration amplitudes produced in different operating stages of washing such like washing process, rinsing process, low-speed dewatering distribution process are different. In the existing drum type washing machine shock absorber, the damping force of the damping is substantially constant at all times, and the change and adjustment of the damping cannot be achieved.
The current widely used shock absorber for the drum washing machine is a friction shock absorber, as shown in FIG. 2. The shock absorber 5′ includes a sleeve 6′, a piston rod 7′ and a friction plate 8′. An end of the sleeve 6′ is connected with the washing, bucket 2′, an opening is provided on the other end of the sleeve 6′. An end of the piston rod 7′ sticks into the sleeve 6′ through the opening, the other end of the piston rod 7′ is connected to the lower portion of the shell 1′ of the washing machine (see FIG. 1), the friction plate 8′ abuts against an inner wall of the sleeve 6′ and comes into contact with an outer wall of the piston rod 7′.
When the washing machine is working, the movement of the washing bucket 2′ drives the sleeve 6′ to move, so the friction plate 8′ fixed to the inner wall of the sleeve 6′ and the piston rod 7′ having one end fixed to the shell 1′ of the washing machine move relatively. Due to the friction principle, the piston rod 7′ produces a damping force on the sleeve 6′, which is determined by the friction coefficient of the friction plate 8′ and the piston rod 7′, and the pressure between the two, and the direction of the damping force is opposite to the direction of the relative movement. The damping force can suppress the excessive vibration of the washing bucket, but due to the principle of force interaction, the sleeve 6′ also produces a reaction force of equal magnitude and opposite direction to the piston rod 7′, which acts on the lower portion of the washing machine shell 1′ to cause the shell 1′ to generate a corresponding vibration.
However, the entire working range of the drum washing machine includes both large amplitude conditions such as washing, rinsing, low-speed dewatering, and small amplitude conditions such as high-speed dewatering. The amplitudes are different even in the various stages of large amplitude conditions such as washing, rinsing, low-speed dewatering. In order to suppress the vibrations in the large amplitude conditions, shock absorber with larger damping force is selected. However, the larger damping force is easy to cause a larger vibration of the shell 1′ of the washing machine in the small amplitude conditions (such as high-speed dewatering), thus it increases the noise of the whole washing machine. And if a shock absorber with smaller damping force is used, the vibration in the large amplitude conditions cannot be suppressed and there is a possibility of machine shift.
A Chinese applicant No. 92204732.4 patent discloses a shock absorber that utilizes magnetic fluid to adjust the damping. The use of magnetic fluid sealing gas principle by the gas as the working medium and the magnetic fluid as a shock absorber damping regulator, and an electromagnet is installed on the shock absorber, the magnetic field generated by the electromagnet acts on the regulator-magnetic fluid. By adjusting the electromagnet current, the magnetic field strength is changed, so that the regulator has different pressure capacity, to achieve the goal of adjusting the damping. To use the shock absorber, it is connected to the vibrating object, when the object is vibrating, the piston produces movement, the increase and decrease of volumes of the upper and lower cavities that are separated by the piston are relatively opposite to each other. And the air pressure decreases in one cavity and increases in the other one, which results in a pressure difference. The magnitude of the pressure difference is related to a clearance between the piston and a cylinder adjusted by the magnetic fluid, and the pressure difference is small when the clearance is big, the pressure difference is big when the clearance is small. The size of the clearance is regulated by the magnetic fluid which is affected under the magnetic field, and the strength of the magnetic field is controlled by the magnitude of the coil current, thus to achieve the purpose of adjusting the pressure difference, that is damping adjustment.
Although the patent mentioned above discloses a technical scheme of utilizing the change of current to change the sealing of the magnetic fluid to the gas, and thus through pressure difference to adjust the damping. But it did not provide the technical scheme of controlling the change of the current, the person having ordinary skill in the art cannot determine how to adjust the current change in real time to adjust the magnitude of the damping force according to the description of the application file. Additionally, the sealing is not reliable using air as the medium of the shock absorber which is costly as well. The electromagnet is fixed to one end of the shock absorber and the sealing of the magnetic fluid is reduced when the piston moves to the far end of the magnet, and the sealing is increased when the piston moves to the near end of the magnet. The damping force of the air through the magnetic fluid is different and the damping tierce cannot be kept constant. And the piston is a moving part, how the magnetic fluid sticks between the piston and the cylinder wall is not stated in the patent. Secondly, the shock absorbing stroke of the shock absorber can only be designed very short, otherwise the magnetic force generated by the magnet may not be applied to the magnetic fluid, which cannot achieve the sealing effect. Besides, the damping force of this shock absorber cannot be too large, because the air is more easily compressed media. Even if the magnetic flow completely sealed air, and the vibration force is large enough, the piston may also be compressed air into liquid.
On the basis of the above patent, the applicant, in the applicant No. 200710065595.9 application, discloses a drum washing machine having a magnetorheological active shock absorber which installs a plurality of magnetorheological active shock absorbers under the washing bucket. The magnetorheological active shock absorber is connected with an electronic control unit and the electronic control unit is connected with a sensor unit to form a close-loop control circuit. Through the sensor to collect the vibration of the washing machine, it can adjust the damping force real-time, and to achieve the purpose of eliminating or reducing the vibration of the washing machine by timely adjusting the damping force of the shock absorber according to the drum washing machine vibration. Although the application has given a specific technical solution tor controlling the current change, it still does not solve the above-mentioned problems of such shock absorbers in the prior art. In addition, the improved magnetorheological active shock absorber has the following disadvantages:
1. An amplitude capturing component, that is the sensor, is added in the control system of the washing machine, and the damping, of the shock absorber is changing in the whole process, which greatly increases the burden on the control system and manufacturing costs, and it is completely unnecessary. In addition, this is an ideal design, which barely can be controlled and achieved;
2. In the magnetic fluid shock absorber described above, the electromagnet is fixed at one end of the shock absorber and cannot effectively control the flowability of the magnetic fluid in the moving position, so that the damping force cannot be accurately controlled;
3. As long as the speed is higher than the resonant frequency of the speed when the washing machine is in operation, with the increase in speed vibration amplitude will be smaller and smaller, and the damping force can be completely eliminated to avoid the vibration of the energy delivered to the shell, so real-time capturing the amplitude and controlling the damping of the shock absorber is also not necessary.
In the view of foregoing, the present disclosure is proposed.